1. Field of Invention
The present invention relates generally to the field of oilfield exploration, production, and testing, and more specifically to casing and casing joints useful in such operations.
2. Related Art
In hydrocarbon production, after a well has been drilled and casing has been cemented in the well, perforations are created to allow communication of fluids between reservoirs in the formation and the wellbore. Any suitable perforating techniques recognized in the industry may be used. Shaped charge perforating is commonly used, in which shaped charges are mounted in perforating guns that are conveyed into the well on a slickline, wireline, tubing, or another type of carrier. The perforating guns are then fired to create openings in the casing and to extend perforations as penetrations into the formation. In some cases wells may include a pre-pack comprising an oxidizer composition, and perforation may proceed through the pre-pack. These techniques may be used separately or in conjunction with shaped charges that include an oxidizer in the charge itself. Any type of perforating gun may be used. A first type, as an example, is a strip gun that includes a strip carrier on which capsule shaped charges may be mounted. The capsule shaped charges are contained in sealed capsules to protect the shaped charges from the well environment. Another type of gun is a sealed hollow carrier gun, which includes a hollow carrier in which non-capsule shaped charges may be mounted. The shaped charges may be mounted on a loading tube or a strip inside the hollow carrier. Thinned areas (referred to as recesses) may be formed in the wall of the hollow carrier housing to allow easier penetration by perforating jets from fired shaped charges. Another type of gun is a sealed hollow carrier shot-by-shot gun, which includes a plurality of hollow carrier gun segments in each of which one non-capsule shaped charge may be mounted.
Other downhole perforating mechanisms are described generally in U.S. Pat. No. 6,543,538. Alternative perforating devices include water and/or abrasive jet perforating, chemical dissolution, and laser perforating for the purpose of creating a flow path between the wellbore and the surrounding formation. There are many disadvantages to current perforating techniques. As explained in this patent, not only is a perforating device required downhole, in many cases an actuating device must be suspended in the wellbore for the purpose of actuating the charges or other devices that may be conveyed by the casing. Each individual gun may be on the order of 2 to 8 feet in length, and contain on the order of 8 to 20 perforating charges placed along the gun tube; as many as 15 to 20 individual guns could be stacked one on top of another such that the assembled gun system total length may be approximately 80 to 100 feet. This total gun length must be deployed in the wellbore using a surface crane and lubricator systems. Longer gun lengths could also be used, but would generally require additional or special equipment. The perforating device must be conveyed downhole by various means, such as electric line, wireline, slickline, conventional tubing, coiled tubing, and casing conveyed systems. The perforating device can remain in the hole after perforating the first zone and then be positioned to the next zone before, during, or after treatment of the first zone. There are numerous other patents describing perforating, but they all require either a mechanical device (such as a sliding sleeve), pumping fluid though a jetting device, perforating guns, or other downhole devices.
In sum there are many disadvantages in conventional perforating techniques, including: safety concerns with explosive charges; the need for conveying equipment to convey the perforating device and actuators, if any, downhole; risk of loss or damage of these devices downhole; time required in deploying the mechanisms downhole. Further, while it is possible to perforate casing downhole at one well location and then move the perforating device within the wellbore to another location and repeat the perforation process, there is the possibility for erring in locating the perforating device, which is disadvantageous. Nevertheless, and despite these and other disadvantages, these downhole perforating techniques are the standard today. There is a need in the art to eliminate or reduce risks, cost, and time of conventional perforating.